Selective communication system between ground station and a plurality of mobile stations



July 4, 1950 l. F. JONES 2,513,490

' SELECTIVE COMMUNICATIO ATION 2 Sheets-Sheet l N SYSTEM BETWEEN GROUND ST AND A PLURALITY 0F MOBILE STATIONS Filed Feb. 28, 1947 lli l nvcmor ZQRENE JNES (lttorneg July 4, 1950 L, F. JoNEs 2,533,490

SELECTIVE COMMUNICATION SYSTEM BETWEEN GROUND STATION AND A PLURALITY 0F NOBILE STATIONS Filed Feb. 28, 1947 2 Sheets-Sheet 2 7'0 Rig/0,41? l A177 Tuo@ AVH? Patented July '4, 1950 SELECTIVE COMMUNICATION SYSTEM BE- TWEEN GROUND STATION AND A PLU- RALITY OF MOBILE STATIONS Loren F. Jones, Philadelphia, Pa., assignor to Radio/Corporation ol.' America, a corporation of Delaware Application February 28, 1947, Serial No. 731,451

4 claims. (on. 343-10) This invention relates to systems for communieating from a ground station selectively to any of a plurality of aircraft.

The principal object of the invention is to provide a communication system adapted for use in conjunction with navigation systems of the type described in copending United States patent application Serial Number 607,9991/2, filed July 31, 1945 by Loren F. Jones, and entitled Radio Navigation System, wherein the visible display produced by a ground-based radio locator system is relayed by television to aircraft within the service area of the ground station. The system described in said copending application is also generally described in an article entitled Teleram Air Navigation and Trailic Control by Means of Television and Radar, published in RCA Review, vol. VII, No. 4, December 1946, pps. 601- 621.

A further object is to provide a system of communication requiring only a single carrier frequency for selective communication with any one of a plurality of aircraft.

Another object is to increase the rapidity with which communication may be established, by eliminating the use of the communication channel for calling or otherwise identifying the craft to be communicated with.

'Ihe invention will be described with reference to the accompanying drawing wherein:

Figure 1 is a schematic block diagram of a navigation system embodying the invention,

Figure 2 is an illustration of a typical display appearing on an aircraft in the operation of the system of Figure l and Figure 3 is a schematic diagram showing a modification of the system of Figure 1.

Referring to Figure 1, the ground station lncludes-a radar system generally designated by the numeral I and provided with a cathode ray position indicator tube 3. A translucent map 5 is placed over the face of the tube 3, and shows the air routes surrounding the ground station, traffic control instructions or other information. A television camera l is directed at the tube 3 and the map 5, and is connected to a television broadcast transmitter 9.

Each aircraft using the complete system is equipped with a television receiver II, responsive to the ground station television transmitter 9 to reproduce the display picked up by the camera 'l on a picture tube I3. In addition, each aircraft may carry a radar transponder beacon, comprising a receiver I5 responsive to the signals sent out by the radar system I, a coding device I I for modifying the received signals in a manner characteristic of the particular craft or of the altitude at which it is flying, and a transmitter I9 for sending the modified signals back to the radar station. 'I'he system thus far described is substantially thc same as that described in more detail in said copending Jones application Serial Number 607,9991/2.

In order to provide for communication from the ground station to aircraft within the service area., a communications transmitter 2l is located in the vicinity of the radar system I. The transe mitter 2| has a sharply directive antenna 23. A receiver IG responsive to the frequency of the transmitter 2l is provided on each aircraft. For two way communication, the aircraft will be equipped with a transmitter and a ground receiver will be provided.

In front of and independent of the map 5 is a transparent disk 25, provided with a slot or other means for supporting and guiding a transparent cursor 2l. The cursor 2l is provided with an opaque cross or similar index. By means of the cursor handle, the disk 25 is rotatable about its center, which coincides with the axis of the indicator tube 3 and is mechanically coupled to the antenna 23 through gearing 29 and a shaft or equivalent means, designated by the dash line 3 I. The arrangement is such that when the disk 25 is positioned so that the line of motion of the cursor 21 extends through a pip on the tube 3, theantenna 23 is directed toward the corresponding aircraft. If the antenna beam is fan shaped, i. e., narrow ln azimuth and broad in elevation, the signals will reach the aircraft at both low and high altitudes.

In the operation of the system, the disk 25 and the cursor 21 are adjusted by means of a handle 33 to place the index mark over the pip in the radar display representing the craft with which communication is to be made. The index mark will appear on the picture tube I3, as shown at 34 in Figure 2. The point 35 represents the location of the ground station. The diagrams 31 and 39 show map details. Various pips indicating the positions of different aircraft appear at 3l, 33, Q5 and M.

The operator on the craft corresponding to the pip 43 will see the index mark over his pip, and will know that he is about to receive a message. The operator on the craft at the position El, in line with the craft #i3 and the ground station, will know that he will hear the message but that it is not for him. Other craft, at other bearings from the ground station, will not hear the message.

To direct the message more specifically to a :,slasoo l 3 singie aircraft, a sharp conical or "penciP beam mavbeusedinplaceofthefanbeam. 'Referring to Figure 3, the antenna 28, in addition to being rotatable in azimuth, is also movable in elevation about the horizontal axis of a shaft v82. ,A plurality of cathode ray tubes la, Ib, and 3c ars connected to the radar l through an altitude layer selector I9 of the type described in the aforementioned Jones application so that each tube provides a display depicting only the aircraft kwithin a respective altitude layer. 'Ihe shaft *I2r is coupled to pinions 98 engaging racks 42 on the cursors associated with the tubes 9a, 9b, and 3c.

The elevation angle of the antenna 23 will be controlled by the radial position of whichever one of the cursors 21 is in use. Since any onenof the tubes 3a, 3b, and 9c will show only pips representing aircraft in respective altitude layers, the distance of a particular pip from the center of the display is an approximate measure of the elevation angle. By placing the index of the cursor over the aircraft pip, as indicated by Il and 49 of Figure 2, the antenna is raised to the proper elevation.

It is apparent that the selective communication system described above will operate in conjunction with any ground surveillance radar, without the use of any equipment in the aircraft except for the receiver Il, providing the pictorial presentation of Figure 2 is not needed. If a fan beam is used, the cursor need move only in rotation. If a sharp conical beam is used, the radial motion of the cursor will have to be retained, and altitude information, whetherv obtained by radar or otherwise, must be combined with distance information (i. e. the radial position of the cursor), to control the elevation angle of the antenna 23.

I claim as my invention:

l. In a radio navigation system including a ground station, radio locator means at said station including means providing a map-like display indicating the positions and relative altitudes of aircraft within the service ar ea of said station, and television means reproducing said display on said aircraft, a system for selective communication from said ground station to any of said craft, including a visible index and means for superimposing said index over the point on said display corresponding to the position of the selected craft; directive transmitter means at said ground station, and means for controlling the direction and elevation of transmission of said directive transmitter means in accordance with the position of said index on said display.

2. In a radio navigation system including av ground station, radio locator means for indicating visually the positions of aircraft within the service area of said ground station, a system for communicating from said ground station selectively to any of said aircraft, including a directive transmitter at said ground station, means for superimposing on said visual display of position indications at said ground station a. further indication of the position of the craft to which com- 4 mlmicationistobenndaandmeans tothepositinnofsaidfurtherlndieaiiononsaid displaytocontrolthedirectionofof said directive transmitter and television pickup and transmitter means for broadcasting to said aircraft a television signal corresponding to the visual indications afforded by said radio locator means and said further indication, and television receiver means on said aircraftfor reproducing `said indications thereon.

3. In a radio navigation system including a ground station, a radio locator system at said ground station including means providing a piurality of map-like dispiaymcorresponding to different altitude layers, of the positions of aircraft within the service area of said station, a system for selective communication from said ground station to any of said craft, including a visible index and means for superimposing said index over the point on one of said map-like displays corresponding to the position of the selected craft; directive transmitter means at said ground station, and means for controlling the azimuth and elevation of the direction of tr n n u of said directive transmitter means in accordance with the position of said index on said display.

4. In a radio navigation system including a ground station, a radio locator system at said ground station including means providing a plurality of map-like displays, corresponding to different altitude layers, of the positions of aircraft within the service area of said station and television means reproducing on each of said aircraft the display corresponding to the altitude layer in which it is flying. a system for selective communication from said ground station to any of said craft, including a visible index and means for superlmposing said index over the point on one of said map-like displays corresponding to the position of the selected craft; directive transmitter means at said ground station, and means for controlling the azimuth and elevation of the direction of transmission of said directive transmitter means in accordance with the position of said index on said display.

LOREN F. JON.

REFERENCES CITED The following references are of record in the ille of this patent:

UNITED STATE PATENTS Number Name Date 733,910 Ladd July 14, 1903 2,027,527 Hammond Jan. 14, 1936 2,027,528 Hammond Jan. 14. 1936 2,152,329 Schussel Mar. 28, 1939 2,234,244 Gossel Mar. 11, 1941 2,307,029 Elm Jan. 5, 1943 2,395,966 Goldberg Mar. 5, 1946 2,401,759 Hersey June 1l, 1946 2,459,481 Woll! et ai Jan. 18, 1949 OTHER REFERENCES "Radio News, pp. 664, ses, 634, sas, my um. 

